Benzo quinoline, 4-hydroxy

UV and pKa measurements show that pyridine-3-thiol and quinoline-3-thiol occur predominantly in the zwitterion form, e.g. (133) (76AHC(S1)144). Quinolines carrying a mercapto group on the benzo ring exist in the zwitterion or the zwitterion extended quinone form to a larger extent than do the analogous hydroxy compounds (63AHC(S1)400). 

H-[Pg.1129]

The nitration of 4-hydroxy-2-methy1-7,8,9,10-tetrahydro benzo[h]quinoline and various other reactions have been described (M. Abbasi et oL., J. heterocyclic Chem., 1978, 15, 649). 

DX-8951/ (l-Amino-9-ethyl-5-fluoro-l,2,3,9,12,15-hexahydro-9-hydroxy-4-methyl-(lS, 9S)-1 OH, 13H-benzo[de ]pyrano[3, 4 6,7]indoKzino[l,2-b ]-quinoline-10,13-dione Methane sulfonate (1 1), Exatecan Mesylate)... 

In general, these properties of hydroxy substituted derivatives will be present in pi-deficient nitrogen heterocycles with benzo fusion or with multinitrogen substitution. For example, the 4-OH group on quinoline tautomerizes to the 4-quinolone structure (Scheme 6.36). 

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